1. Field of the Invention
The present invention is broadly concerned with a method for the recovery of aqueous and organic solvent-based printing ink wastes, which are generated in considerable volume in commercial printing operations, in order to greatly minimize the environmental problems attendant to treatment and disposal of such wastes. More particularly, it is concerned with such a method of ink waste recovery wherein waste ink sludge is first rendered flowable and then directed into a hydroheater simultaneously with high pressure steam, in order to subject the ink wastes to conditions of elevated temperature, pressure and intense shear, and thus create a processed output. Alternately, dilute ink washup wastes may be directly treated in a hydroheater without preliminary chemical treatments to obtain a desirable processed output. These outputs can then be dried and powdered, and the resultant product can be used in the formulation of ink for reuse. Alternately, the hydroheater output may be passed through a filter press to yield a pressed cake, which can subsequently be dispersed and formulated as an ink.
2. Description of the Prior Art
Operators of printing equipment must periodically clean the inking assemblies associated with such equipment, either at the end of a shift or when a new printing run is to be set up and made ready. Ink assembly cleaning typically involves spraying the inking assembly with water and/or other appropriate solvents which is thereafter collected as ink waste. Wastes of this character include relatively large volumes of water, together with pigment particles and ink carriers.
Increasingly stringent environmental regulations prohibit direct disposal of ink wastes. Accordingly, it is common practice to treat such washup wastes with cationic and/or anionic polymers as necessary, so that the solids fraction of the ink wastes may be readily separated. The solids fraction is then allowed to drain for periods on the order of twenty-four hours, thereby forming a sludge normally containing 10-20% solids therein, and including ink solids, surfactants, the previously employed separation polymers, and varnishes.
Despite these steps, however, disposal of ink sludges presents significant problems. In some locales, the sludges may be placed in a landfill, although this option is becoming both expensive and of limited viability. Another approach is to subject the sludges to pyrolytic destruction. Although pyrolytic treatment is effective, it is a very expensive proposition, both from the standpoints of fuel consumption and shipping to the destruction site.
As a consequence of these intractable problems, printers both large and small are increasingly concerned about the costs associated with lawful disposal of their printing ink wastes; and there is a very significant need in the art for a low cost process for recovering such ink wastes.